32 NORMAL HISTOLOGY. 



Ciliated Cells from the Trachea of the Dog, The tra- 

 chea is carefully removed from a recently killed dog and 

 slit up, longitudinally, along its posterior surface. It is 

 then pinned out on a piece of sheet cork and treated in 

 the same manner as the rabbit's bladder. 



Ciliary Movement in Living Ciliated Cells from the Frog's 

 Month. The mucous membrane of the roof of the mouth 

 of a living frog is gently scraped with a scalpel, and the 

 slimy mass thus procured is transferred to a large drop 

 of one-half-per-cent. salt solution on a slide, and thor- 

 oughly teased apart. The specimen is now covered, a bit 

 of hair being placed beforehand beside it to prevent pres- 

 sure from the cover-glass. The cells are mostly sphe- 

 roidal, and will be seen isolated or in clusters ; the cilia, 

 in the form of rows of delicate hair-like processes, spring- 

 ing from one side of the cells. A considerable number 

 of non-ciliated cells will also be observed. The form of 

 the cilia will be most readily seen in cells in which the 

 movement is becoming languid, which occurs gradually 

 in all, and finally ceases altogether. The movement, when 

 vigorous, often causes cells and masses of cells to revolve 

 and move about in the fluid, and frequently produces 

 currents in the latter, into which floating particles are 

 drawn and then driven onward with considerable velocity. 



